feat: Implement systematic format logic documentation injection

[AMDphreak]

This PR introduces a centralized 'Format Logic' page and updates the Ddoc preprocessor to automatically inject formatting guidance into relevant Phobos function documentation. See the new format.dd for the centralized guide.

[dlang-bot]

Thanks for your pull request and interest in making D better, @AMDphreak! We are looking forward to reviewing it, and you should be hearing from a maintainer soon.
Please verify that your PR follows this checklist:

• My PR is fully covered with tests (you can see the coverage diff by visiting the details link of the codecov check)
• My PR is as minimal as possible (smaller, focused PRs are easier to review than big ones)
• I have provided a detailed rationale explaining my changes
• New or modified functions have Ddoc comments (with Params: and Returns:)

Please see CONTRIBUTING.md for more information.

---

If you have addressed all reviews or aren't sure how to proceed, don't hesitate to ping us with a simple comment.

Bugzilla references

Your PR doesn't reference any Bugzilla issue.

If your PR contains non-trivial changes, please reference a Bugzilla issue or create a manual changelog.

[CyberShadow]

Hi, so... is there a rationale for why we want to do this?

The new page and the injectFmtLogic approach are a bit awkward, and I'm not sure it belongs in this repository since it's a bit of a Phobos concern.